Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C59: Ballistic Transport in Semiconductor DevicesLive
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Sponsoring Units: FIAP Chair: Son Le, National Institute of Standards and Technology |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C59.00001: Fractional quantized conductance in quasi-one dimensional electrons Sanjeev Kumar, Michael Pepper, David A Ritchie, Ian Farrer In a typical one-dimensional (1D) quantum wire the quantized conductance is in units of 2e2/h. Apart from the 0.7(2e2/h) conductance anomaly there were hardly any additional structures observed until recently when a quasi-1D quantum wire showed appearance of several fractional conductance states in the absence of quantizing magnetic field [1]. In this work, we show that when a 1D quantum wire was relaxed from symmetry to highly asymmetric confinement potential close to the 1D-2D transition, conductance plateaux with both even and odd denominators such as 1/6, 1/2 and 2/5 were produced (in units of e2/h). A 10 T in-plane magnetic field introduced an additional plateau at 2/7 as a function of increasing asymmetry in confinement potential. We will discuss recent results where the Coulomb interactions between electrons create correlated motion and cyclic current which result in backscattering and so the emergence of fractional conductance states [1-3]. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C59.00002: Atomic tunneling in crystalline BaTiS3 Raphael Hermann, Michael E Manley, Barry Winn, Katharine Page, Austin Minnich, Jaeyun Moon, Ahmet Alatas, Jayakanth Ravichandran BaTiS3 exhibits a hexagonal perovskite structure comprised of columns of sulphur coordinated Ti linked by barium making it a quasi-1D structure. Neutron pair distribution function measurements reveal that the Ti atomic displacement parameters increase with decreasing temperature. This observation suggest proximity to a ferroelectric type phase transition or ground-state dynamic disorder. By combining inelastic x-ray scattering phonon spectroscopy and high-resolution inelastic neutron scattering we find evidence for the dynamic disorder scenario for Ti occupying a double-well potential. These dynamics persist into the quantum regime and atomic tunneling with 0.4 meV tunneling splitting is observed. This unique tunneling dynamics has profound consequences on the thermal conductivity and suggest a novel mechanism for thermal transport design. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C59.00003: Mapping Confinement Potential in a Quasi-1D Electron System Servin Rathi, Sanjeev Kumar We investigate the channel potential profiles in a one-dimensional (1D) electron gas defined by a pair of split-gate and a top gate on the surface of GaAs/AlGaAs heterostructure. It has been observed that at low carrier concentration and weak confinement, the ground state conductance doubles in a 1D wire due to the ground state splitting into two separate rows each contributing 2e2/h [1,2]. Various factors including electron-electron interactions and formation of hybridized ground energy states possibly explain the relaxation in the second dimension. We will show the role of confinement potential in modulating the electrons configuration in the channel by solving Poisson-Schrodinger equations. A correlation between the potential in the channel and the appearance of double row electron configuration at various top and split gate voltage combinations has been studied and compared with the experimental results. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C59.00004: Conductance quantization and finite-size effects in cleaved edge overgrowth GaAs quantum wires Henok Weldeyesus, Christian Scheller, Taras Patlatiuk, Gilad Barak, Amir Yacoby, Loren Pfeiffer, Ken W. West, Dominik Zumbuhl Cleaved Edge Overgrowth (CEO) quantum wires (QW) are among the cleanest 1D systems available, showing conductance quantization and Luttinger liquid effects such as charge fractionalization and spin-charge separation. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C59.00005: Quantized Conductance in a One-Dimensional Ballistic Oxide Nanodevice Alexis Jouan, G. Singh, Edouard Lesne, Diogo Vaz, Manuel Bibes, Agnès Barthélémy, Christian Ulysse, Daniela Stornaiuolo, Marco Salluzo, Simon Hurand, Jerome Lesueur, Cheryl Feuillet-Palma, Nicolas Bergeal The electric-field effect control of two-dimensional electron gases (2DEG) has allowed nanoscale electron quantum transport to be explored in semiconductors. Structures based on transition metal oxides have electronic states that favour the emergence of novel quantum orders that are absent in conventional semiconductors and the 2DEG formed at a LaAlO3/SrTiO3 interface —a structure in which superconductivity and spin–orbit coupling can coexist— is a promising platform to develop devices for spintronics and topological electronics. However, field-effect control of the properties of this interface at the nanoscale remains challenging. In this presentation we show that a quantum point contact can be formed in a LaAlO3/SrTiO3 interface through electrostatic confinement of the 2DEG using a split gate. Our device exhibits a quantized conductance due to ballistic transport in a controllable number of one-dimensional conducting channels. Under a magnetic field, the direct observation of the Zeeman splitting between spin-polarized bands allows the determination of the Landé g-factor, whose value differs strongly from that of free electrons. Through source–drain voltage measurements, were also performed a spectroscopic investigation of the 3d energy levels inside the quantum point contact. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C59.00006: Disorder information from conductance: a quantum inverse problem shardul mukim, Mauro S Ferreira It is straightforward to calculate the conductance of a quantum device once all its scattering centers are fully specified. However, to do this in reverse, i.e., to find information about the composition of scatterers in a device from its conductance, is an elusive task. This is particularly more challenging in the presence of disorder. We propose a procedure in which valuable compositional information can be extracted from the seemingly noisy spectral conductance of a two-terminal disordered quantum device. In particular, we put forward an inversion methodology that can identify the nature and respective concentration of randomly-distributed impurities by analyzing energy-dependent conductance fingerprints. Results are shown for graphene nanoribbons as a case in point using both tight-binding and density functional theory simulations, indicating that this inversion technique is general, robust and can be employed to extract structural and compositional information of disordered mesoscopic devices from standard conductance measurements. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C59.00007: Transverse magnetic focusing as measurement tool for electron-electron interactions in GaAs/AlGaAs Jean J. Heremans, Adbhut Gupta, Gitansh Kataria, Mani Chandra, Saeed Fallahi, Geoff C Gardner, Michael Manfra The mesoscopic and ballistic phenomenon of transverse magnetic focusing (TMF) is investigated in a two-dimensional electron system in a high-mobility GaAs/AlGaAs heterostructure at low temperatures 0.4 K < T < 20 K (electron mean free path ~ 68 μm at 4.2 K) using precision nonlocal measurements and high-resolution kinetic simulations. Measurements feature a distance between the injector and collector of 7 μm. The measured TMF amplitude of the nonlocal resistance plotted versus T shows a monotonic decrease as T is increased from 4.2 K to 20 K. A characteristic decay length is extracted by fitting experimental data with an exponential fit, and shows a 1/T2 dependence, indicating a dominant role for inelastic electron-electron interactions in limiting TMF amplitude. The simulations, which reveal both cyclotron orbits and current vortices, confirm the experimental observations and determine that the decay length relates to the momentum-conserving electron-electron scattering length. The combined experiments and simulations provide a direct way to measure the momentum-conserving scattering length in a TMF setting. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C59.00008: Hydrodynamic and ballistic transport over large length scales in GaAs/AlGaAs Adbhut Gupta, Jean J. Heremans, Gitansh Kataria, Mani Chandra, Saeed Fallahi, Geoff C Gardner, Michael Manfra Hydrodynamic and ballistic transport regimes are investigated through nonlocal resistance measurements and high-resolution kinetic simulations in a mesoscopic structure on a high-mobility 2D electron system in a GaAs/AlGaAs heterostructure over a temperature range 4 K < T < 40 K, at zero magnetic field. The nonlocal measurements are performed in a large-scale (∼30 × 24 μm) ultraclean (electron mean free path ∼ 65 μm at 4.2 K) device, which by its scale offers exceptional sensitivity to electron-electron scattering, featuring 10 point contacts to probe voltages at various distances from the current injection contacts. The one-to-one simulations, involving the actual experimental geometry in the precise contact configuration, and taking into account both momentum relaxing and momentum conserving scattering, determine that the device transitions from a predominantly ballistic regime at T= 4.2 K to a hydrodynamic regime at T ≈ 10...15 K. The combined experiments and simulations reveal the existence of collective transport phenomena in both regimes, highlighting that negative nonlocal resistance and current vortices are not exclusive to the hydrodynamic regime. |
Monday, March 15, 2021 4:36PM - 4:48PM Live |
C59.00009: High-performance, electrolyte-gated vertical organic nanoscale transistors Jakob Lenz, R. T. Weitz
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Monday, March 15, 2021 4:48PM - 5:00PM Live |
C59.00010: Kinetic Inductance in Ballistic Transport Jashan Singhal, Debdeep Jena Electron transport in nanoscale semiconductors approaches the ballistic limit. Without scattering, the kinetic inductance of carriers becomes considerably large. Using a generalized formulation of ballistic transport, we investigate the generalized kinetic inductance in a d-dimensional conductor with various band-structures (e.g. parabolic and conical) in the ballistic limit. The kinetic inductance per unit length is evaluated as a function of carrier density and temperature at low bias voltages. Kinetic inductance is found to very weakly depend on voltage, and strongly on the electron density. An increase in kinetic inductance at low density is expected because more velocity is needed to maintain the same current. The ballistic model predicts that even without considering phonon scattering, the kinetic inductance decreases at high temperature. Because of the Fermionic nature of electrons, their collective excitation exhibits a Newtonian inertia, which decreases with an increase in temperature. The quantum mechanical ballistic kinetic inductance is compared to the standard classical inductance in the Boltzmann Transport regime, and its importance is classified for various carrier densities, and dimensions. |
Monday, March 15, 2021 5:00PM - 5:12PM Live |
C59.00011: Current vortices in ballistic transport: Collective motion without interactions Mani Chandra, Gitansh Kataria
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Monday, March 15, 2021 5:12PM - 5:24PM Live |
C59.00012: Quantum tunneling in the dice lattice irradiated with circularly polarized light Dipendra Dahal, Godfrey Anthony Gumbs We investigate the properties of quantum tunneling across a smooth square electrostatic potential barrier in the dice model irradiated with circularly polarized light. The resulting time-dependent Hamiltonian is reduced to an effective Hamiltonian with the use of the Floquet-Magnus high-frequency expansion valid off-resonance. The flat band is located at the center of the bandgap band and is not affected by irradiation. The linear dispersion in the dice model is modified in the presence of the irradiation, leading to the destruction of the Klein tunneling for normal incidence. It is demonstrated that the additional irradiation term, in general, suppresses the transmission. We investigate the conditions for super-Klein tunneling when there is perfect transmission over a wide angle of incidence. We also report our results for the ballistic conductance as the energy gap is modified by the irradiation. |
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